LMV321M7 National Semiconductor, LMV321M7 Datasheet - Page 17

• Manufacturer Part Number: LMV321M7
• Description: OPERATIONAL AMPLIFIER OP AMP IC
• Manufacturer: National Semiconductor

Specifications of LMV321M7

• No. Of Amplifiers: 1
• Slew Rate: 1V/µs
• No. Of Pins: 5
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• Amplifier Type: Operational
• Package / Case: 5-SC-70
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Notes
For minimum dc offset, V
inverting and non-inverting inputs should be equal, which
means
From Equation (1) and Equation (8), we obtain
The values of C
As a design example:
Require: A
Start by selecting C
is close to
From Equations (6), (7), (9), (10),
The above resistor values are normalized values with ω
1rad/s and C
frequency and resistances to the real values, two scaling
factors are introduced, frequency scaling factor (k
pedance scaling factor (k
Scaled values:
LP
1
= 2, Q = 1, fc = 1KHz
= C
1
2
and C
= C
1
R
R
C
and C
2
3
1
n
= R
= R
= C
2
= 1F. To scale the normalized cut-off
m
+
are normally close to or equal to
R
R
R
R
).
= V
1
4
2
1
2
3
4
2
. Choose a standard value that
= 1Ω
= 1Ω
= 4Ω
= 4Ω
= 15.9 kΩ
= 63.6 kΩ
= 0.01 µF
−
, the resistor values at both
(Continued)
f
) and im-
(10)
n
(8)
(9)
=
17
An adjustment to the scaling may be made in order to have
realistic values for resistors and capacitors. The actual value
used for each component is shown in the circuit.
4.4.3 2nd-order High Pass Filter
A 2nd-order high pass filter can be built by simply inter-
changing those frequency selective components (R
C
shown in Figure 14, resistors become capacitors, and ca-
pacitors become resistors. The resulted high pass filter has
the same corner frequency and the same maximum gain as
the previous 2nd-order low pass filter if the same compo-
nents are chosen.
4.4.4 State Variable Filter
A state variable filter requires three op amps. One conve-
nient way to build state variable filters is with a quad op amp,
such as the LMV324 (Figure 15).
This circuit can simultaneously represent a low-pass filter,
high-pass filter, and bandpass filter at three different outputs.
The equations for these functions are listed below. It is also
called "Bi-Quad" active filter as it can produce a transfer
function which is quadratic in both numerator and
denominator.
1
FIGURE 14. Sallen-Key 2nd-Order Active High-Pass
, C
2
) in the Sallen-Key 2nd-order active low pass filter. As
Filter
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10006083
1
, R
2
,